At least one person was killed and two others injured when a roadside bomb exploded in Egypt's second largest city, Alexandria.

The blast Tuesday, which killed a 27-year-old man, occurred just hours after two explosive devices were discovered at different terminals at Cairo's international airport. Both were defused.

Another blast also went off in the center of the capital without casualties. A security official was quoted as saying that the device was a sound bomb.

No groups have claimed responsibility for any of the bombs, but Islamist militants frequently target security personnel throughout Egypt in retaliation for the government's crackdown on the outlawed Muslim Brotherhood.

The Egyptian government is also battling an insurgency in the Sinai Peninsula, base to the group Sinai Province, an affiliate of the Islamic State formerly known as Ansar Beit al Maqdis.

Map of Egypt

Last week, the group claimed responsibility for coordinated attacks in the Sinai Peninsula which killed more than 30 security personnel.

Egypt has been trying to project an image of stability ahead of an investment conference in the resort of Sharm el-Sheik in March that the government hopes will generate ventures worth billions of dollars.

Political turmoil and militant violence after the 2011 uprising that toppled autocrat Hosni Mubarak have hammered tourism, a pillar of the economy.